Continuous feed vibratory finishing machine with discharge rate controlled by operation of tub discharge closure

ABSTRACT

A vibratory finishing machine including a supporting frame, a processing tub, and a tub vibrating mechanism interposed between the frame and the tub. A continuous feed finishing operation is provided by charging the workpieces and media into one end of the tub and discharging them through an opening in the opposite end of the tub. The bottom of the discharge opening extends substantially level with the bottom of the tub thereby providing no obstruction which will cause liquids or other materials to be retained for excessive times within the tub. A power-operated closure is mounted on the tub for selectively closing and opening the discharge opening. The closure is movable toward and away from the discharge opening along a path generally perpendicular to the opening to control the discharge of materials from the tub, thereby controlling the retention time of the materials in the tub.

United States Patent 9 Rampe Aug. 27, 1974 [75] Inventor: John F. Rampe, Mayfield Heights,

Ohio

[73] Assignee: Rampe Research, Cleveland, Ohio [22] Filed: July 11, 1972 [2]] App]. No; 270,700

Related US. Application Data [63] Continuation-impart of Ser. No. 8.815. Feb. 5, 1970,

Pat. No. 3,685,213.

Primary ExaminerHarold D. Whitehead Attorney, Agent, or FirmWatts, Hoffmann, Fisher & Heinke ABSTRACT A vibratory finishing machine including a supporting frame, a processing tub, and a tub vibrating mechanism interposed between the frame and the tub. A continuous feed finishing operation is provided by charging the workpieces and media into one end of the tub and discharging them through an opening in the opposite end of the tub. The bottom of the discharge opening extends substantially level with the bottom of the tub thereby providing no obstruction which will cause liquids or other materials to be retained for excessive times within the tub. A poweroperated closure is mounted on the tub for selectively closing and opening the discharge opening. The closure is movable toward and away from the discharge opening along a path generally perpendicular to the opening to control the discharge of materials from the tub, thereby controlling the retention time of the materials in the tub.

19 Claims, 6 Drawing Figures CONTINUOUS FEED VIBRATORY FINISHING MACHINE WITH DISCHARGE RATE CONTROLLED BY OPERATION OF TUB DISCHARGE CLOSURE CROSS REFERENCE TO RELATED PATENTS AND APPLICATION The present application is a continuation in part of application Ser. No. 8815 filed Feb. 5, 1970 now issued as US. Pat. No. 3,685,213, dated Aug. 22, 1972 hereinafter the Continuous Feed Patent.

Finishing Apparatus, Pat. No. 3,3 1 8,951 issued May 9, 1967 to John F. Rampe hereinafter the Finishing Patent.

Finishing Apparatus, U.S. Pat. No. 3,337,997 issued Aug. 28, 1967 to John F. Rampe, hereinafter the Orbital Patent.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to abrasive finishing machines and more particularly to a vibratory finishing machine of the continuous feed type having a discharge system for controlling the retention time of workpieces within the tub of the machine.

2. Prior Art Vibratory finishing machines adapted to smooth and finish the surfaces of workpieces by such operations as deburring, burnishing, descaling, and cleaning are well known. Such machines commonly employ a processing tub adapted to receive a quantity of workpieces and abrasive finishing media. The tub is then vibrated to impart a finishing action to the workpieces.

As brought out in the referenced patents, the abrasive media can conveniently be separated from the workpieces after the media and workpieces are discharged from the tub. After separation, the finishing media may then be returned to the tub of the finishing machine for re-use. The finishing liquid is usually drained off during separation of the media and workpieces. The finished workpieces are subsequently collected and conveyed to a separate unit or group of units for washing, drying, inspection and packaging.

Various proposed continuous feed vibratory finishing machines are also known. Such proposed machines provide the processing tub with spaced charging and discharging devices whereby media and workpieces enter one end of the tub and are subjected to a finishing action as they progress through the tub for discharge at the opposite end.

One problem with prior proposals for continuous feed vibratory finishing machines is that the time during which workpieces are retained in the tub is not readily controllable. Workpieces of a relatively soft metal, or workpieces needing only minimal deburring, etc., require only a short retention time. workpieces of harder metal which have many large burrs to be removed, will require longer retention times. Hence, where the retention time requirements differ from that provided by prior art continuous feed finishing machines, it has previously been necessary to operate the finishing machine on a batch process basis where the retention time can be carefully controlled.

One problem which has been occasioned with the apparatus described in the referenced Continuous Feed Patent, is that the weir structure forming the bottom lip of the discharge opening tends to trap and cause the undesirable buildup of some materials, particularly liquids, within the finishing machine tub. Periodically the machine must be shut down and undesirable materials cleaned out of the tub.

SUMMARY OF THE INVENTION The present invention overcomes the foregoing drawbacks of the prior art finishing machines and provides a finishing machine with a discharge system for controlling the retention time of workpieces in the tub of the machine.

The finishing machine of the present invention may be operated on a batch basis if so desired but is designed primarily for continuous operation according to a pre-arranged time schedule. Pursuant thereto, a discharge system is provided including a closurecontrolled discharge opening the bottom of which is not substantially higher than the bottom of the finishing machine tub whereby no obstruction is provided which will cause the accumulation of materials in the tub.

It has been found that the retention time of workpieces in the tub can adequately be controlled without a weir type discharge opening by carefully controlling the operation of the discharge closure. One of the advantages of the invention resides in the flexibility of the closure operating cycle, which can be adjusted by the operator from time to time to lengthen or shorten the retention time of materials within the tub. The discharge closure can be opened and closed by a timing control device preset to selected intervals of operation.

Once the closure operating cycle has been decided upon, the operator adjusts the timing mechanism to provide the predetermined retention periodtypically l0 seconds-for processing the workpieces constituting part of the contents of the tub. This is normally followed by a release period-typically 5 secondsfor partial discharge of materials from the tub. This cycle of closure operation is continually repeated and establishes an effective rate of discharge of materials from the tub which determines the retention time of workpieces in the tub. In some cases, the nature of the workpieces may call for longer or shorter processing times than those mentioned above; in such instances, the operator can readily re-set the timing mechanism to provide correspondingly longer or shorter retention periods preceding the release periods.

In the operation of the machine, the charging apparatus supplies the tub as required with suitable abrasive processing media. An aqueous finishing liquid is usually introduced concurrently therewith to facilitate finishing of the workpieces. The workpieces themselves are added by the operator. For all practical purposes, the operation of the charging apparatus is, in effect, keyed to that of the discharge system and simply returns the abrasive media which has been discharged from the tub back into the tub.

In accordance with one aspect of the present invention, the discharge system includes a discharge structure projecting from one end of the tub and defining a discharge opening which is inclined slightly upwardly to correspond with the approximate angle of inclination of the leading surface of materials as they discharge from the tub. A' door structure is provided which is movable into and out of registry with the discharge opening along a path which is generally perpendicular to the discharge opening. The door is guided by a pair of guide rods disposed on opposite sides thereof. A pneumatically operated bellows is provided to effect closure movements of the doors structure. A pair of compression coil springs carried on the guide rod bias the door to the open position and are operative to collapse the bellows when the bellows is vented to atmo sphere by a timer controlled valve.

Accordingly, it is the principle object of the present invention to provide a vibratory finishing machine including an improved discharge system for controlling the retention time of workpieces in the processing tub, and a method of performing finishing operations.

Other objects and a fuller understanding of the inven" tion may be had by referring to the following description and claims taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of an orbital finishing machine within the perview of the present invention;

FIG. 2 is a top plan of the machine on a somewhat larger scale;

FIG. 3 is a side elevational view showing on a still larger scale the discharge closure assembly at the end of the tub seen at the right in FIGS. 1 and 2, with the discharge closure in open position FIG. 4 is a corresponding vertical section as seen from the plane indicated by the line 44 in FIG. 2, with the discharge closure in closed position;

FIG. 5 is a view on the same scale as FIG. 3 as seen from the plane indicated by the line 55 in FIG. 3; and

FIG. 6 is a view on the same scale as FIG. 3 as seen from the plane indicated by the line 6-6 in FIG. 3.

DESCRIPTION OF PREFERRED EMBODIMENT Referring to FIGS. 1 and 2, a finishing machine 10 constructed in accordance with the present invention includes a platform 11 which supports a motor 12. A chain belt drive system 13 couples the motor 12 to a vibration inducing system (not shown) of the type described in the referenced Orbital Patent for vibrating a tub 20. A guard 14 shields the chain belt drive system. A shroud l5 encloses much of the understructure of the machine 10.

Adjoining the shroud 15 is a console 16 which mounts a control box 17. A conventional timing mechanism l8 programmable by an operator in a manner which will be described is housed within the control box 17.

The tub 20 is generally cylindrical in shape and is supported from beneath as described in the Orbital Patent. A wide, longitudinally extending opening 21 is defined by mutually diverging wings 22 formed on the tub 20. A plurality of cross heads 23 bridge the space separating the wings 22.

A generally square end plate 24 is aligned with the tub 20 at its charging end, the left end as seen in FIG. 2. A central circular opening of substantially the same diameter as the tub 20 is formed through the end plate 24 to admit finishing media to the tub 20. A hopper 25 is attached to the end plate 24 for feeding plastic or stone finishing media through the opening in the end plate 24 and into the tub 20. An elongated top opening 26 is formed in the hopper. The top opening 26 receives finishing media dropped from the upper end of a bucket conveyor 27.

The conveyor 27 is mounted in a framework 28 supported by suitable uprights 29. A motor 30 supplies power to the conveyor 27 near its upper end. The lower end of the conveyor 27 is supported within a housing 31. The conveyor 27 provides a means of returning media discharged from the machine 10 back into the tub 20 for re-use.

A square end plate 34 is mounted on the right end of the tub 20, as viewed in FIG. 2. the end plate 34 has a central aperture which is in alignment with the bottom of the tub such that finishing media, finished parts, abrasive chips, liquids, and such other materials as may be present in the tub 20 can be discharged without obstruction. A discharge structure 38 communicates with the aperture in the plate 34 and defines a discharge opening 39. A power operated closure system, indicated generally by the numeral 40 is provided to selectively open and close the end of the discharge opening 39.

Referring to FIGS. 3 and 4, the end plate 34 is secured to the end of the tub structure 20 by fasteners 35. A resilient sheet 36 of tub lining material is interposed between the tub structure 20 and the plate 34. The end plate 34 and the tub lining sheet 36 have aligned apertures as shown at 37 in FIG. 4.

The discharge structure 38 is welded to the plate 34 and communicates with the apertures 37 to provide a smooth conduit for the discharge of materials from the tub 20. The bottom of this discharge conduit is level with the bottom of the tub 20 so that it does not obstruct the discharge of materials from the tub 20.

The outer end 39 of the discharge structure 38 extends in a plane inclined at an angle of approximately 30 from the vertical and has exit surfaces defining an inclined discharge opening 39. By inclining the plane of the discharge opening 39 in this manner, the discharge opening tends to lie in nearly the same plane as the leading surface of materials discharging from the tub structure 20. A power operated closure 40 including a bellows 45 operates to selectively open and close the discharge opening 39.

The closure system 40 includes a heavy metal frame welded to the end plate 34. The supporting frame includes a pair of V-shaped side plates 41, 42 welded to the end plate 34, and a crossmember 43 welded to the side plates 41, 42. A pair of fasteners 44 extend through apertures formed in the crossmember 43 and mount a pneumatically actuated bellows 45.

The bellows 45 preferably comprises such a bellows as is sold by Firestone Tire and Rubber Company of Akron, Ohio under the designation Airide 268. The bellows 45 is expansible during inflation from the deflated configuration shown in FIG. 3 to the inflated configuration shown in FIG. 4. A conduit 46 extends through an aperture in the cross-member 43 for supplying air to and exhausting air from the bellows 45.

A movably mounted closure assembly 47 is secured by fasteners 48 to the other end of the bellows 45, as is best seen in FIGS. 4 and 6. The closure assembly 47 includes a resilient closure lining sheet 49 adhered to a channel-shaped mounting plate 50. The lining sheet 49 facilitates the formation of a liquid tight seal when the closure 40 is closed against the discharge structure 38.

A pair of bushings 51, 52 are mounted in apertures formed through the plate 50. The bushings 51, 52 slidably received a pair of guide rods 53, 54. The inner ends of the guide rods 53, 54 are received within apertured bosses 55 formed on the end plate 34. The outer ends of the guide rods 53, 54 extend through apertures formed in the crossmember 43 and are threaded to receive nuts 56. The guide rods are disposed along opposite sides of the path of travel at the closure assembly 47 to guide the movement of the closure assembly 47.

Movement of the closure assembly toward and into contact with the discharge structure 38 is effected by inflating the bellows 45. Movement of the closure assembly to the open position of FIG. 3 is effected by a pair of compression coil springs 57, 58 mounted on the guide rods 53, 54. The springs 57 58 engage the bosses 55 at one end and engage the bushings 51, 52 at the other end. When the bellows 45 is inflated with sufficient pressure, the biasing action of the springs 57, 58 is overcome and the closure assembly 47 is caused to move toward the discharge structure 38. When the pressure within the bellows 45 is released, the springs 57, 58 move the closure assembly 47 to the open position, collapsing the bellows and exhausting air through the conduit 46.

The timing mechanism 18 is arranged in conventional fashion to operate an air valve 60. In one selectable position, the valve 60 serves to admit compressed air from a conduit 61 to the conduit 46 for inflating the bellows 45. In another selectable position, the valve 60 serves to vent the conduit 46 to atmosphere permitting the collapse of the bellows 45 under the influence of the springs 57, 58. The timing mechanism 18 is preferably programmable to cyclically operate the valve 60 to open and close the closure 40 for selected intervals of time.

Materials discharging through the opening 39, drop into a substantially horizontally disposed trough 65. The trough 65 is provided just above its bottom with an inclined fine mesh screen 66. The openings in the screen 66 are small enough to prevent the passage at workpieces and finishing media therethrough while allowing the entrained finishing liquid to separate and drip through to the bottom of the trough 65. The finishing liquid may be recirculated. if desired, or simply allowed to drain into a collecting vessel or sewer. In the meantime, the workpieces and finishing media are urged toward the far end of the screen 66 by gravity and/or forces imposed on them by subsequently discharging tub contents.

At the remote end of the trough, the screen 66 is equipped with a wide-mesh insert 67 that allows the media, but not the workpieces, to drop through the insert 67 and into the lower end of conveyor 27. The conveyor 27 carries the finishing media toward its upper end for return to tub through hopper 26. The workpieces are precluded by the widemesh insert 67 from dropping through this portion of the screen, and move onto an inclined run-off tray 68. The workpieces then fall by gravity into a waiting tote box or other receptacle.

In normal operation, the workpieces, together with the desired type or types of media, are vibrated in the tub 20, with the closure 40 in the closed position, for a selected retention period. The closure 40 is then opened permitting the tub contents, consisting of the workpieces media and fluid, etc., spill out through the opening 39 into trough an onto screen 66. After a suitable discharge interval, the timing mechanism 18 operates to move the closure 40 to its closed position.

The retention time of the workpieces in tub 20 can be increased or decreased by adjusting the timing mechanism 18 in accordance with the type of materials being finished.

Although the invention has been described in its preferred form with a certain degree of particularity, it is understood that the present disclosure of the preferred form has been made only by way of example and numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and the scope of the invention as hereinafter claimed.

What is claimed is:

l. A continuous feed vibratory finishing machine comprising:

a. a supporting frame structure;

b. a tub structure carried on said frame structure but free to vibrate relative to said frame structure;

c. a vibration producing mechanism interposed between said structures to vibrate said tub structure;

d. charging means for substantially continuously feeding workpieces to be finished and. finishing media into said tub structures;

e. discharging means spaced from the charging means for controllably discharging workpieces and media from said tub structure at a substantially continuous rate; I

f. said discharging means comprising:

i. opening means defining a discharge opening in communication with said tub structure, the bottom of said discharge opening being substantially no higher than the bottom of said tub structure whereby the contents of the tub structure can be discharged without obstruction;

. closure means movable toward and away from said opening means along a linear path substantially perpendicular to said discharge opening for selectively closing and opening said discharge opening whereby said said closure means may be opened to discharge materials from the tub through said discharge opening in an unobstructed fashion and may be closed to retain workpieces and media within said tub structure; and iii. closure operator and flow control means connected to said closure means for cyclically moving said closure means toward and away from said opening means to open and close said discharge opening during the operation of said machine thereby to control the retention time of workpieces within the tub.

2. The vibratory finishing machine of claim 1 wherein said closure operator and flow control means includes a timing control to open and close said closure means at predetermined intervals of time during the operation of the machine, whereby the retention time of workpieces within the tub is controlled by the timing control:

3. The vibratory finishing machine of claim 1 wherein:

a. said opening means comprises wall portions extending longitudinally from a discharge end portion of the tub structure and having exit surfaces defining a discharge opening exit; and,

b. said closure means comprises a generally planar door structure movable into and out of registry with said surfaces.

4. The vibratory finishing machine of claim 3 wherein:

a. said door structure is translatable toward and away from said discharge opening along a path which is generally perpendicular to the plane of said exit surfaces; and,

b. said closure means additionally includes guide means engaging said door structure for guiding the movement of said door structure along said path.

5. The vibratory finishing machine of claim 4 wherein said closure operator and flow control means includes:

' a. biasing means biasing said door structure to an open position out of registry with said exit surfaces; and,

b. fluid operated means operable under the influence of pressurized fluid to overcome the operation of said biasing means and to move said door structure toward and into registry with said exit surfaces.

6. The vibratory finishing machine of claim 5 wherein:

a. said guide means comprises a pair of guide rods disposed one on either side of said door structure and journaled by said door structure for sliding movement of said door structure along said guide rods; and,

b. said biasing means comprises a pair of compression coil springs each disposed around a separate 7 one of said guide rods and engaging said door structure.

7. The vibratory finishing machine of claim 5 wherein said fluid operated means comprises a pneumatically operated bellows expansible under the influence of compressed air to move said door structure along said guide means and into registry with said exit surfaces.

8. The vibratory finishing machine of claim 3 wherein the plane of said exit surfaces is inclined from the vertical so as to face generally upwardly whereby the plane of said exit surfaces at least approximates the angle of inclination of the lead surface of a quantity of materials discharging from said opening and said closure is movable along a path generally perpendicular to said plane.

9. A continuous feed vibratory machine comprising:

a. a supporting structure resiliently supporting a tub together with means for vibrating said tub relative to the supporting structure;

b. charging means and discharging means arranged to substantially continuously introduce into and discharge from said tub at spaced regions of the tub such materials as workpieces and finishing media, whereby said machine is operable in a continuous feed mode;

c. said discharge rate control means including:

i. a closure movable selectively into and out to registry with said discharge opening along a linear path substantially perpendicular to said discharge opening;

ii. closure operator means connected to said closure for effecting movement of said closure along said path; and

iii. closure operator control means connected to said closure operator means for cyclically controlling the opening and closing of said closure to control the retention time of workpieces with the tub.

10. The vibratory finishing machine of claim 9 wherein said closure operator control means comprises programmable means operable to effect opening and closing of said closures in accordance with a preselected cycle of operation.

11. The vibratory finishing machine of claim 9 wherein said wall portions have exit surfaces defining an upwardly facing discharge opening disposed at an angle inclined from the vertical which at least approximates the angle of inclination of the lead surface of a quantity of materials discharging from said tub, and said closure comprises a door structure movable toward and away from said discharge opening along a path which is generally perpendicular to said exit surfaces.

12. A vibratory finishing machine comprising:

a. a supporting frame structure;

b. a tub structure carried on said frame structure but free to vibrate relative to said frame structure;

c. a vibration producing mechanism interposed between said structures to vibrate said tub structure;

(1. charging means for feeding workpieces to be finished and finishing media into said tub structure; e. discharging means spaced from the charging means for controllably discharging workpieces and media from said tub structure; f. said discharging means comprising:

i. a series of connected wall portions forming exit surfaces defining a discharge opening in communication with said tub structure, the bottom of said discharge opening being substantially no higher than the bottom of said tub structure whereby the contents of said tub structure can be discharged through said discharge opening without obstruction.

ii. closure means for selectively opening and closing said discharge opening whereby workpieces and finishing media can be selectively retained in said tub structure or discharged through said discharge opening;

iiiv said closure means including a door structure adapted to register with said exit surfaces to close said discharge opening, and guide means for guiding the movement of said door structure along a path which is generally perpendicular to the plane of said discharge opening; and,

iv. closure operator and flow control means connected to said closure means for moving said closure means along said path toward and away from said opening means to open and close said discharge opening during the operation of said machine thereby controlling the retention time of workpieces within the tub, said closure operator and flow control means including biasing means biasing said door structure to an open position out of registry with said exit surfaces and fluid operated means operable under the influence of pressurized fluid to overcome the operation of said biasing means and to move said door structure toward and into registry with said exit surfaces.

13. The vibratory finishine machine of claim 12 wherein:

a. said guide means comprises a pair of guide rods disposed one on either sideof said door structure for guiding the movement of said door structure therealong; and,

b. said biasing means comprises at least one compression coil spring biasing said door structure away from said discharge opening.

14. The vibratory finishing machine of claim 12 wherein said fluid operated means comprises a bellows expansible under the influence of compressed air to move said door structure along said guide means and into registry with said exit surfaces.

15. In a vibratory finishing machine of the type including a receptacle adapted to receive finishing media together with workpieces to be finished, and vibratory drive means for vibrating the receptacle to effect a finishing operation on the workpieces, the improvement of a closure assembly for selectively opening and closing a discharge opening formed in one wall of the receptacle. said closure assembly comprising:

a. a closure movable selectively into and out of registry with receptacle wall portions defining the discharge opening to selectively open and close the discharge opening;

b. guide means supporting said closure for movement along a linear path substantially perpendicular to the discharge opening toward and away from the discharge opening between and open position and a closed position;

c. biasing means biasing said closure toward one of said positions;

(1. power drive means connected to said closure and being operable to overcome the action of said biasing means to move said closure to the other of said positions.

16. The apparatus of claim 15 wherein the plane of the discharge opening is oriented to correspond substantially to the plane of the leading edge of materials which discharge through the discharge opening from the finishing machine. receptacle.

17. The apparatus of claim 15 wherein said biasing means biases said closure to said open position, and said power dirve means is operable to overcome the action of said biasing means to move said closure into registry with receptacle wall portions defining the discharge opening. I

18. The apparatus of claim 15 wherein said power drive means comprises a pneumatic bellows.

19. The apparatus of claim 15 wherein the finishing machine is of the continuous feed type, and a closure control system is provided to cyclically operate said power drive means to repetitively open and close said closure in accordance with a cycle of operation which will effect retention of the workpieces in the receptacle for a desired length of time.

N D STA'IES PATEN'I (unquej CERTI FICATE OF CORREC'LLON 3,831,322 Dated August 27 1974 ,Patent No.

Inventor(s) John F. Rampe It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

- Column 1, ine 11, delete "3,318,951" andsubst'itute Column 4, line llffdelete "the" and substitute I The Signed a nd sealed tis 91: day of November 1974.

(@SEAL) Attest:

McCOY M. GIBSON JR. Attesting Office:

c. MARSHALL DA 'N Commissioner of Patents- FORM PO-lOSO (10-69) 

1. A continuous feed vibratory finishing machine comprising: a. a supporting frame structure; b. a tub structure carried on said frame structure but free to vibrate relative to said frame structure; c. a vibration producing mechanism interposed between said structures to vibrate said tub structure; d. charging means for substantially continuously feeding workpieces to be finished and finishing media into said tub structures; e. discharging means spaced from the charging means for controllably discharging workpieces and media from said tub structure at a substantially continuous rate; f. said discharging means comprising: i. opening means defining a discharge opening in communication with said tub structure, the bottom of said discharge opening being substantially no higher than the bottom of said tub structure whereby the contents of the tub structure can be discharged without obstruction; ii. closure means movable toward and away from said opening means along a linear path substantially perpendicular to said discharge opening for selectively closing and opening said discharge opening whereby said said closure means may be opened to discharge materials from the tub through said discharge opening in an unobstructed fashion and may be clOsed to retain workpieces and media within said tub structure; and iii. closure operator and flow control means connected to said closure means for cyclically moving said closure means toward and away from said opening means to open and close said discharge opening during the operation of said machine thereby to control the retention time of workpieces within the tub.
 2. The vibratory finishing machine of claim 1 wherein said closure operator and flow control means includes a timing control to open and close said closure means at predetermined intervals of time during the operation of the machine, whereby the retention time of workpieces within the tub is controlled by the timing control.
 3. The vibratory finishing machine of claim 1 wherein: a. said opening means comprises wall portions extending longitudinally from a discharge end portion of the tub structure and having exit surfaces defining a discharge opening exit; and, b. said closure means comprises a generally planar door structure movable into and out of registry with said surfaces.
 4. The vibratory finishing machine of claim 3 wherein: a. said door structure is translatable toward and away from said discharge opening along a path which is generally perpendicular to the plane of said exit surfaces; and, b. said closure means additionally includes guide means engaging said door structure for guiding the movement of said door structure along said path.
 5. The vibratory finishing machine of claim 4 wherein said closure operator and flow control means includes: a. biasing means biasing said door structure to an open position out of registry with said exit surfaces; and, b. fluid operated means operable under the influence of pressurized fluid to overcome the operation of said biasing means and to move said door structure toward and into registry with said exit surfaces.
 6. The vibratory finishing machine of claim 5 wherein: a. said guide means comprises a pair of guide rods disposed one on either side of said door structure and journaled by said door structure for sliding movement of said door structure along said guide rods; and, b. said biasing means comprises a pair of compression coil springs each disposed around a separate one of said guide rods and engaging said door structure.
 7. The vibratory finishing machine of claim 5 wherein said fluid operated means comprises a pneumatically operated bellows expansible under the influence of compressed air to move said door structure along said guide means and into registry with said exit surfaces.
 8. The vibratory finishing machine of claim 3 wherein the plane of said exit surfaces is inclined from the vertical so as to face generally upwardly, whereby the plane of said exit surfaces at least approximates the angle of inclination of the lead surface of a quantity of materials discharging from said opening and said closure is movable along a path generally perpendicular to said plane.
 9. A continuous feed vibratory machine comprising: a. a supporting structure resiliently supporting a tub together with means for vibrating said tub relative to the supporting structure; b. charging means and discharging means arranged to substantially continuously introduce into and discharge from said tub at spaced regions of the tub such materials as workpieces and finishing media, whereby said machine is operable in a continuous feed mode; c. said discharge rate control means including: i. a closure movable selectively into and out to registry with said discharge opening along a linear path substantially perpendicular to said discharge opening; ii. closure operator means connected to said closure for effecting movement of said closure along said path; and iii. closure operator control means connected to said closure operator means for cyclically controlling the opening and closing of said closure to control the retention time of workpieces with the tub.
 10. The vibratory finishing machine Of claim 9 wherein said closure operator control means comprises programmable means operable to effect opening and closing of said closures in accordance with a preselected cycle of operation.
 11. The vibratory finishing machine of claim 9 wherein said wall portions have exit surfaces defining an upwardly facing discharge opening disposed at an angle inclined from the vertical which at least approximates the angle of inclination of the lead surface of a quantity of materials discharging from said tub, and said closure comprises a door structure movable toward and away from said discharge opening along a path which is generally perpendicular to said exit surfaces.
 12. A vibratory finishing machine comprising: a. a supporting frame structure; b. a tub structure carried on said frame structure but free to vibrate relative to said frame structure; c. a vibration producing mechanism interposed between said structures to vibrate said tub structure; d. charging means for feeding workpieces to be finished and finishing media into said tub structure; e. discharging means spaced from the charging means for controllably discharging workpieces and media from said tub structure; f. said discharging means comprising: i. a series of connected wall portions forming exit surfaces defining a discharge opening in communication with said tub structure, the bottom of said discharge opening being substantially no higher than the bottom of said tub structure whereby the contents of said tub structure can be discharged through said discharge opening without obstruction. ii. closure means for selectively opening and closing said discharge opening whereby workpieces and finishing media can be selectively retained in said tub structure or discharged through said discharge opening; iii. said closure means including a door structure adapted to register with said exit surfaces to close said discharge opening, and guide means for guiding the movement of said door structure along a path which is generally perpendicular to the plane of said discharge opening; and, iv. closure operator and flow control means connected to said closure means for moving said closure means along said path toward and away from said opening means to open and close said discharge opening during the operation of said machine thereby controlling the retention time of workpieces within the tub, said closure operator and flow control means including biasing means biasing said door structure to an open position out of registry with said exit surfaces and fluid operated means operable under the influence of pressurized fluid to overcome the operation of said biasing means and to move said door structure toward and into registry with said exit surfaces.
 13. The vibratory finishine machine of claim 12 wherein: a. said guide means comprises a pair of guide rods disposed one on either side of said door structure for guiding the movement of said door structure therealong; and, b. said biasing means comprises at least one compression coil spring biasing said door structure away from said discharge opening.
 14. The vibratory finishing machine of claim 12 wherein said fluid operated means comprises a bellows expansible under the influence of compressed air to move said door structure along said guide means and into registry with said exit surfaces.
 15. In a vibratory finishing machine of the type including a receptacle adapted to receive finishing media together with workpieces to be finished, and vibratory drive means for vibrating the receptacle to effect a finishing operation on the workpieces, the improvement of a closure assembly for selectively opening and closing a discharge opening formed in one wall of the receptacle, said closure assembly comprising: a. a closure movable selectively into and out of registry with receptacle wall portions defining the discharge opening to selectively open and close the discharge opening; b. guide meaNs supporting said closure for movement along a linear path substantially perpendicular to the discharge opening toward and away from the discharge opening between and open position and a closed position; c. biasing means biasing said closure toward one of said positions; d. power drive means connected to said closure and being operable to overcome the action of said biasing means to move said closure to the other of said positions.
 16. The apparatus of claim 15 wherein the plane of the discharge opening is oriented to correspond substantially to the plane of the leading edge of materials which discharge through the discharge opening from the finishing machine. receptacle.
 17. The apparatus of claim 15 wherein said biasing means biases said closure to said open position, and said power dirve means is operable to overcome the action of said biasing means to move said closure into registry with receptacle wall portions defining the discharge opening.
 18. The apparatus of claim 15 wherein said power drive means comprises a pneumatic bellows.
 19. The apparatus of claim 15 wherein the finishing machine is of the continuous feed type, and a closure control system is provided to cyclically operate said power drive means to repetitively open and close said closure in accordance with a cycle of operation which will effect retention of the workpieces in the receptacle for a desired length of time. 